the dte-facsimile dce communications link shall provide full duplex character data at rates fast enough to accommodate the transfer of synchronous t.30 phase c data.12,000 bit/s is the minimum rate needed to support 9600 bit/s v.29 phase c data. 19,200 bit/s is sufficient to support v.29 signaling at 9600 bit/s. with flow control, it is not necessary, and not recommended, to change the dte-dce communications link data rate during facsimile operation.

    flow control is necessary to match the dte-dce data rate to the line signaling rate and to the requirements of group 3 data transmission. (for example, provision must be made for minimum scan line times.) in band unidirectional dc1/dc3 (xon/xoff) flow control is mandatory; flow control using v.24 circuits 106 and 105 is optional. in the verbose format, result code responses are preceded by the ascii characters [cr][lf], and followed by [cr][lf].in the non-verbose format ,result code responses are preceded by no characters, and followed by a single [cr].

    the ascii [dle] character (hex $10) is used as a special character, to shield special characters. the [dle][etx] character pair (hex $10, hex $03) is used to mark the end of a stream. the following patterns are used:

    any data [dle] [etx] end of stream

    any data [dle] [dle]... single $10 in data stream

    any data [dle] [not dle or etx] delete both [dle] & next character